Here’s a detailed guide to what you should check when buying a used Doosan PUMA TT1800SY (twin-turret, twin-spindle, Y-axis, mill/turn turning center). These machines are complex, so you want to do a fairly thorough inspection to avoid big costs later.

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Key Specs / What to Know First

Before you begin inspection, know approximately what the machine should have—so you can spot deviations or missing features. Some of the standard specs (which may vary by region / options) are:

Spec	Typical Value
Chuck size	8″
Max turning diameter	~ 230 mm (≈ 9″)
Bar capacity / max bar work diameter	~ 65mm ≈ 2.6″
Spindle speed	~ 5000 rpm
Spindle motor power	~ 22 kW for main spindles in the 30 minuter duty class; somewhat lower for continuous duty.
Travel / axes: X1, X2, Z1, Z2, Y‐axis, etc.	X1 ~ 165 mm; X2 ~ 190 mm; Z travels ~ ~700 mm; Y is ±50 mm (100 mm total) for the upper turret in the SY version.
Rapid traverse rates / LM guideways etc.	Fast rapid traverse (Z & A axes ~ 40 m/min) etc. Roller or linear guideways for many axes.

Knowing these helps judge if what you’re inspecting is close to “factory spec” or has been modified/worn.

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What to Inspect Mechanically & Structurally

Because the TT1800SY is a high-productivity, high complexity multi-tasking machine, problems tend to be more expensive. Here are what to check physically / mechanically:

1. Spindles (Left & Right)
   • Check for run-out (radial and axial). Use test bars or dial indicators.
   • Listen for bearing noise or roughness when spinning idle.
   • Check spindle taper and nose: wear, damage, corrosion.
   • Through-spindle coolant features: presence, condition, leaks.
2. Turrets (Upper & Lower)
   • Indexing accuracy and speed: does it index cleanly, quickly; any chatter or misalignment?
   • Tool stations: check for wear, damage (e.g. to BMT tool holders, live tooling stations).
   • Turret alignment: ensure when turret rotates, all stations center properly; check alignment in all axes.
3. Y-Axis Function (Upper Turret)
   • On the SY version, the upper turret has a Y-axis (± about 50 mm). Check that Y travel is smooth, backlash is minimal, and homing works reliably.
   • Make sure motion is accurate, linear guides or slides for Y are not worn or damaged.
4. Axes & Guideways
   • Check X1, X2, Z1, Z2 movements full Travel. Look for binding, loss of smoothness, slop or backlash.
   • Inspect guideways (box ways, LM or roller guideways) for signs of wear, rust, scoring.
   • Check ball screws: any play, backlash, or damage.
   • Thermal issues: cooling systems for spindles / slideways; are oil jackets, coolant/chiller systems working?
5. Control System / Electronics
   • Which control is installed (Fanuc, etc.) and version. Are there known software bugs / maintenance issues?
   • Homing & limit switches for all turrets and axes: do they work reliably? (Some users report upper turret X, Y homing failures or misalignment issues).
   • Inspect wiring, encoders, motor / servo drives for signs of overheating, damage or maintenance.
6. Cooling, Lubrication, Oil / Maintenance Systems
   • Hydraulic/lubrication systems: check oil quality, filters, whether units are clean or contaminated.
   • Coolant systems, chip conveyors, parts catcher or unloader: are they present, operational, clean?
   • Spindle cooling, if present, should be checked: leaks, performance, governor etc.
7. Structural Integrity of the Machine Base / Casting
   • Check for cracks in castings, damage from shocks or crashes.
   • Check machine is still square (turrets place tool precisely relative to spindle etc.).
   • Look for signs the machine has been abused (e.g. bumps, metal chips accumulation, poor cleaning).
8. Safety Features
   • Guards, interlocks, emergency stops, access panels etc. should be intact and functional.
   • Check whether safety standards compliance (local / international) is satisfied or can be made so.

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Known / Common Issues & What To Ask The Seller

From existing user reports and forums, here are things that people have reported or had issues with—worth asking about or specifically checking:

• Some alignment issues over time, especially with turrets: turrets can get knocked accidentally, or wear in guideways, leading to misalignment.
• Homing problems: in some machines the upper turret X and Y axes may not home properly due to sensor / switch misalignment or failure.
• Tool load monitoring / load monitoring systems: check whether they are still functioning; these help avoid tool breakage and unexpected downtime.
• LM or roller guideways may degrade if maintenance (lubrication, cleaning) has been neglected.
• Wear on the turrets’ indexing system: how well they rotate, how precisely they index to stations.
• Electronics & control updates: older firmware, worn out components.
• Thermal drift: since these machines are expected to do high volume production, cooling systems (spindle, motor, guideways) matter a lot for maintaining accuracy over long runs.

You should ask the seller:

• What is the hour meter / usage (how many hours in machining / spindle hours).
• Has it had any crashes, collisions (turret vs part, etc.)?
• When was maintenance done last (spindle bearings, coolant, lubrication, guideways)?
• Are there records (service logs)?
• Does everything operate under load (run a test part)?
• Are all accessories included (tooling, chucks, parts catcher, conveyors)?
• Is the machine still under warranty or covered by support (spare parts) for control/electrics etc.?

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Practical / Operational Considerations

• Transport & Installation Costs: These machines are large, heavy, and delicate (turrets, precision alignment). Moving and re-installing can be expensive.
• Foundation, Leveling, Utilities: Ensure you have the correct power supply, proper cooling, ventilation, space. Foundations must be solid and well aligned.
• Spare Parts Availability: Even though Doosan is a big brand, certain parts (especially for turrets, live tooling, control) may have long lead times or be expensive.
• Software / Licensing: If control or software needs updating (or if certain options are licensed), check those costs.
• Operator Training: These are complex machines—dual spindles, dual turrets, Y-axis, etc. If your lab/shop doesn’t have familiar operators, there will be a learning curve.